I. Field of the Invention
This invention relates generally to pulmonary performance testing equipment, and more particularly to an improved, disposable, single-use patient valve employed in the breathing circuit of such equipment.
II. Discussion of the Prior Art
In an earlier U.S. Pat. No. 5,119,825 to James Huhn and entitled "Multi-Functional Patient Valve", which is assigned to the assignee of the present application, there is described a single-use, disposable patient valve for use in cardiopulmonary test apparatus comprising a molded, flexible, elastomeric tubular body of a cruciform shape and cooperating with the stem portion of the cross are first and second selectively actuable clamps which, when actuated, pinch off the flow of gases across the pinched portions. The full teaching and description of the patient valve described in that aforereferenced patent are hereby incorporated by reference.
As is fully explained in U.S. Pat. No. 5,119,825, a procedure called lung diffusion is used in accessing a patient's lung volume. In this procedure, the cruciform shape elastomeric patient valve has a patient mouthpiece having a flow measuring capability connected to one end of its stem and the opposite end is open to the ambient. A gas demand valve is coupled to a first end of the patient valve's cross member while the opposite end of this cross member is coupled to a gas sample apparatus. In use, a first clamp is actuated for pinching the patient valve to block off ambient air and, during the patient's inspiratory phase, a test gas, such as a mixture of carbon monoxide and neon, is inhaled through the demand valve, through the multi-functional patient valve, and through the mouthpiece into the patient's lungs. Now, a second clamp is actuated pinching off the patient valve between the mouthpiece and the valve's cross member such that the patient is made to hold the inhaled gas sample within the lungs for a predetermined time interval. Following this time interval, the second clamping means is released while the first is maintained. The patient may now exhale, with the expired gases passing through the patient valve into the sample chamber. The first clamping means is then released allowing the patient to breathe ambient air. The collected gas sample can be analyzed to determine the capacity of the lungs to absorb oxygen.
Those skilled in the art can appreciate that during use, and especially during the expiratory phase of the testing cycle, the demand valve and the coupling hoses leading to the sample chamber are exposed to the patient's respiratory gases, including moisture particles entrained in the expired gas stream. While the patient valve itself is a single-use, disposable item, it is intended that the demand valve and the coupling equipment utilized to join the patient valve to the sample chamber are intended to be reusable. Noting that bacteria and other infectious germs or viruses may be resident in the moisture particles exhaled by one patient, it is imperative that a means be provided for maintaining isolation of the demand valve circuit from exhaled breath and the mouthpiece from exposure to flow from the sample chamber during inhalation so that a subsequent patient undergoing similar testing will not be exposed to bacteria and germs from a prior patient.
It is accordingly a principal object of the present invention to provide an improved single-use, disposable patient valve of the type described in the aforereferenced Huhn patent, with a means for isolating the demand valve circuit from a given patient's expiratory gases and that patient from the flow of air or other gases from the sampling circuit when inhaling to thereby inhibit the possibility of a infection by a subsequent patient using the equipment, albeit with a new patient valve installed.